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XArray: Fix xa_release in allocating arrays

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xa_cmpxchg() was a little too magic in turning ZERO entries into NULL,
and would leave the entry set to the ZERO entry instead of releasing
it for future use.  After careful review of existing users of
xa_cmpxchg(), change the semantics so that it does not translate either
incoming argument from NULL into ZERO entries.

Add several tests to the test-suite to make sure this problem doesn't
come back.

Reported-by: Jason Gunthorpe <jgg@ziepe.ca>
Signed-off-by: Matthew Wilcox <willy@infradead.org>
This commit is contained in:
Matthew Wilcox
2019-02-20 11:30:49 -05:00
parent f818b82b80
commit b38f6c5027
3 changed files with 48 additions and 22 deletions
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28
lib/test_xarray.c
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@@ -361,6 +361,7 @@ static noinline void check_reserve(struct xarray *xa)
{
void *entry;
unsigned long index;
int count;
/* An array with a reserved entry is not empty */
XA_BUG_ON(xa, !xa_empty(xa));
@@ -377,15 +378,15 @@ static noinline void check_reserve(struct xarray *xa)
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* cmpxchg sees a reserved entry as NULL */
/* cmpxchg sees a reserved entry as ZERO */
XA_BUG_ON(xa, xa_reserve(xa, 12345678, GFP_KERNEL) != 0);
XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, NULL, xa_mk_value(12345678),
GFP_NOWAIT) != NULL);
XA_BUG_ON(xa, xa_cmpxchg(xa, 12345678, XA_ZERO_ENTRY,
xa_mk_value(12345678), GFP_NOWAIT) != NULL);
xa_release(xa, 12345678);
xa_erase_index(xa, 12345678);
XA_BUG_ON(xa, !xa_empty(xa));
/* But xa_insert does not */
/* xa_insert treats it as busy */
XA_BUG_ON(xa, xa_reserve(xa, 12345678, GFP_KERNEL) != 0);
XA_BUG_ON(xa, xa_insert(xa, 12345678, xa_mk_value(12345678), 0) !=
-EBUSY);
@@ -398,9 +399,27 @@ static noinline void check_reserve(struct xarray *xa)
XA_BUG_ON(xa, xa_reserve(xa, 6, GFP_KERNEL) != 0);
xa_store_index(xa, 7, GFP_KERNEL);
count = 0;
xa_for_each(xa, index, entry) {
XA_BUG_ON(xa, index != 5 && index != 7);
count++;
}
XA_BUG_ON(xa, count != 2);
/* If we free a reserved entry, we should be able to allocate it */
if (xa->xa_flags & XA_FLAGS_ALLOC) {
u32 id;
XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_value(8),
XA_LIMIT(5, 10), GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != 8);
xa_release(xa, 6);
XA_BUG_ON(xa, xa_alloc(xa, &id, xa_mk_value(6),
XA_LIMIT(5, 10), GFP_KERNEL) != 0);
XA_BUG_ON(xa, id != 6);
}
xa_destroy(xa);
}
@@ -1486,6 +1505,7 @@ static int xarray_checks(void)
check_xas_erase(&array);
check_cmpxchg(&array);
check_reserve(&array);
check_reserve(&xa0);
check_multi_store(&array);
check_xa_alloc();
check_find(&array);